1. Field of the Invention
The invention relates to an automatic steering apparatus, and more particularly to steering control when disturbance torque is applied during automatic steering.
2. Description of the Related Art
Automatic steering apparatuses have been proposed to run a vehicle along a desired running line. For example, Japanese Patent Laid-Open Publication No. Hei 5-50932 discloses a mechanism which calculates a steering pattern for avoiding a collision and turns a steering shaft to run a vehicle according to the steering pattern. And, if a driver steers a steering wheel to exceed a prescribed angle during the automatic steering, steering by the driver is restricted by an electric motor to secure running according to the steering pattern.
Restriction of the driver's steering operation by the electric motor is not, however, preferable because a system becomes complicated and the driver suffers from an undesired load. Also, when the vehicle is turning by the automatic steering, the driver might hold the steering wheel to hold his or her position. In such cases, automatic turning of the steering wheel is not preferable.